Lacrimal apparatus: Lacrimal gland, Lacrimal canaliculi, Lacrimal sac, Nasolacrimal duct
- A system containing the orbital structures for tear production and drainage.
- Consists of:
- Lacrimal gland
- Lacrimal canaliculi
- Lacrimal sac
- Nasolacrimal duct
- Paired almond-shaped glands, one for each eye
- Secretes the aqueous layer of the tear film.
- Situated in the upper, outer portion of each orbit.
- It is lodged in the lacrimal fossa of the orbit formed by the frontal bone.
- Has palpebral portion and orbital portion
- Palpebral portion lies close to the eye.
- Orbital portion contains fine interlobular ducts that unite to form 3 – 5 main excretory ducts, joining 5 – 7 ducts in the palpebral portion before the secreted fluid may enter on the surface of the eye.
2.Lacrimal puncta and canaliculi
- There are two lacrimal puncta in the medial (inside) portion of each eye.
- Collect tears and conveys to lacrimal sac through lacrimal canaliculi.
- Lacrimal canaliculi are small channels in each eyelid that commence at lacrimal puncta.
- superior duct, the smaller and shorter of the two, at first ascends, and then bends at an acute angle, and passes medialward and downward to the lacrimal sac.
- inferior duct at first descends, and then runs almost horizontally to the lacrimal sac.
- At the angles they are dilated into ampullæ
- Lacrimal sac is the upper dilated end of the nasolacrimal duct
- Lodged in a deep groove formed by the lacrimal bone and frontal process of the maxilla.
- It connects the lacrimal canaliculi, which drain tears from the eye’s surface, and the nasolacrimal duct, which conveys this fluid into the nasal cavity.
- oval in form
- measures from 12 to 15 mm. in length
- upper end is closed and rounded
- lower end is continued into the nasolacrimal duct.
- Carries tears from the lacrimal sac into the nasal cavity. Excess tears flow through nasolacrimal duct which drains into the inferior nasal meatus.
- Duct is lined by stratified columnar epithelium containing mucus-secreting goblet cells, and is surrounded by connective tissue.
- Obstruction of the nasolacrimal duct leads to the excess overflow of tears called epiphora